Electric resistance welding method



June 21, 1949. J. w. BROWN, JR

ELECTRIC RESISTANCE WELDING METHOD Filed July 15, 1947 Y INVENTOR. JOHN W. BROWNJR BY I A TTOPNEYS.

Patented June 21, 1949 OFFICE" aunts-i 'EnEeTmo RnsIsrhNoE WEIEDINGIMETHOD* JohmW. Brown, Jri ,-Lakewood 1 ohm; ,a ssi gnortto. Brown Fintube Company; Elyria, Ohio, va corp'oration of Ohio npplibanoh -July rs; 1947; Serial No. 761,115

(stew-10) I ZCIaims.

v Thisinvention relates o a method for: welding fins and like-thin steel members toathicker steelplate or sheet, and more :particularly'toamethod for simultaneously Welding together two pairs of members 1 eachconsisting of a fin and a plate, by- ,aseries of r-esistance welds: formed during oontinuous relative motion of: the: fins and 1 plates a'sta unitary assembly with respect to opposedroller welding electrodes.

t attempting toweld fins and like-members; one side-ofasteel plate by means of conv'em t'i'onalfl seam welding ma'chinesembodying roller electrodes difii'culties frequently'i are incurred: be-; cause theplate is burned and pitted onthe side opposite the this as a result of-the'conoentration o'f welding current where one of the electrodes engages the" plate. In passing a r-oller electrode over a steel plate the former tends to become fdiile'fdj v'vith steel picked up: from the plate. and

lnustlfre'quently" be cleaned According to'the present inventiomthe above and other difficuleities are eliminated and the welding operationis carried out expeditiously. and eflicientlyin-a oonvennonal seam welder embodying vertically aligned roller electrodes by placing two steel plates back to back and separatedbya plate ofcopper" or other materialfof like softness and electrical properties and then placing.- the steel fins against thesteelplates and engaging the fins by'tl'ieres'pe'ctive electrodes; The two'pairs o'f ,plates'and fins and the intervening copperplate are clamped together as a unitary assemmy andfcurrent passes, from one to the other electrode'through afin and its associated steel plate and, then through the copper to the other steelplate and its fin, and then into the other electrode"; The. Contact areas through which, the Welding currentfiows between the copper plate and thes'teel plates are' lalrgethus eliminating-e15 ce's'slve concentration o'f 'ele'ctric current and heat on the surfaces of. the steel plates opposite the surfaces whicnare? being Welded to the fins Burning pitting of the undersides' of the platesby'the' welding current are thusefiecti-vel y prevented. The} general object of'the invention toprovide an improved method of simultaneously forming." welds between twomembers, of one: pair another. weld between two members of another. pair-ornate]: member-5% with asingle pair ofiroller weldingeelectrodesr, Another object-I ofthe invention isto provide an improvedmethod of:simultaneously welding two thin steel,

fin members-to tWo thicker steel plate 'members respectively without unduly burning or pitting the plate members along the reeionof the welds. Another object is-the provision:- of such a methodwhich can I be carried outtina conventional seam welder having two, sul'lstantial-lyv identical rol1er= electronics.- .A' stillfurther object ofthe inven tion is to provide such a methodinwhich the fins, steelplates and a copper ba-ckingrplate are moved continuously asan assembly relative; to

a" pair of rollerelectrodes during: a substantially continuous: welding; operation; Other objects ofthe invention will become apparent from thefollowing: description and the attached drawing. The novelfeatures of the invention are summarizedintheclaimsi, I

lln thedrawings: Figure l is an enduelevation oi a -group oftfins We-lded-to a-platein accord.- ance with the present-invention; Figure 2 is asideelevation showin an assembly of two-fins. two steel plates and" a coppen plate-betweenethe steel plates all positionedbetween-the, roller electrodes used in the welding. operation and: Figure 3' is a/section -through Figure 2 as-indicated bythe 1inos3 --3 thereon In Figure 1 there. is illustrated one form 0t structure Whose; parts maybewelded together by the,methodot thepresent invention, although it-will beapparentothershapes may be secured together inlike mannei within thescope ofthis invention'whichds limited solelyby the. appended claims. The assembly illustrated comprisesa plate |-0-whichis part ofa-steel chann'elaunithaving sides; H: and I2 forming: the exterior wall ofa conduit: of. a heat-exchanger of a type disclosed and claimed in my copending, application Serial No.-= 7405.98;- Insidefi ofthe channel shapedpor tion andsecuredtothe flat bottom thereof are aseries of sheet steel heat conducting-fins is in theformofchannels havin flanges Hi and bottoms I 1. Complementary facesof each of the bottoms I! and of the plate [0 areqse'cured: to get-he rby a series of resistance welds 20 (Figure 1 TheWelds-IO are formed as a: series by" the use: of continuously rotating: vertically aligned roller: electrodes 22 and: 23': mounted! on: parallelaxes and adapted to clamp between them with appropriate resilient welding pressure two fins [5 and two plates in as shown in Figures 2 and 3. Interposed between the two steel plates I is a copper plate 25 that forms no part of the completed and welded unit but is used as a tool in conjunction with the rollers 22 and 23 properly to distribute current to the region of the welds.

As an example of a procedure which I have found to be satisfactory in welding low carbon steel channel section fins l of a thickness of about .031 inch to a low carbon steel l2 gauge plate H]; the bases of two channel members consisting of an assembly as outlined above are engaged with electrodes 22 and 23 each having a width approximately equal to the width of a channel base with an electrode pressure of 900 to 1000 pounds. The current employed is alternating current at about 12000 amperes and six to eight volts. A weld is made between each pair of fins and plates simultaneously with a duration of current of three cycles of sixty cycle, single phase, alternating current, the current being shut off between welding periods for a period of three cycles between welds. The fins are welded to the plate at a speed of eighteen to twenty feet per minute. Under these conditions the sides of the plates opposite the fin are discolored, but are not unduly pitted or weakened.

The fins I5, plate 10 and copper plate are held as an assembly with respect to each other by any suitable clamping means and the assembly is guided between the eelctrode rollers 22 and 23 by engagement of the edges of the plate 25 with three pairs of grooved rollers 21. The manner of supporting and guiding the assembly is illustrative only and is not to be regarded as limiting the scope of the invention. During the welding operation the rollers 22 and 23 are urged toward each other with the appropriate welding pressure to clamp between them the bases ll of the fins [5, the plates l0 and the copper plate 25.

The welding pressure used is sufficient to force the plates l0 and the soft copper plate 25 together in firm electrical contact over a relatively large area, much greater than the area that would be afforded by the line contact between an electrode roller and a plate I0 if no copper plate 25 was interposed between them. The copper plate is an excellent conductor and current may travel between steel plates I0 and copper plate 25 throughout a substantial area; this distribution of current eliminates concentration of the current and provides a path of low resistance. As a result the outer surfaces of the plates H! in contact with the copper plate 2.5 do not become heated to a sufficiently high temperature to be pitted or otherwise deformed with resultant destruction of the desired finished surface.

Current travels between the fins l5 and the welding electrodes in such manner that there is no appreciable harmful effect on the surface of either. The copper, being relatively soft, deforms under the pressure of the'electrodes and the area of contact between the plates in and the copper plate 25 is increased by this deformation, thus reducing the resistance to flow of current between the electrodes and minimizin the heating effect.

After an assembly comprising two fins I5, two plates 10 and copper plate 25 has been moved be tween the pair of roller weldin electrodes from one end to the other, a succeeding fin is clamped in place against each plate In and the newly formed assembly i moved transversely to the electrode rollers so they will traverse the region in which the series of welds between the succeeding fins and plates are to be made. In most cases, and particularly when the adjacent fins of each plate are parallel to each other, one fin will be welded in place as the assembly traverses the rollers in one direction and the succeeding fin will be welded in place durin the return travel.

From the foregoing description it will be evident that I have provided an improved method of welding together relatively thin fins and sheets without causing any burning or pitting of the exposed surfaces where the welding current leaves the assembly. My method can be carried out in any conventional seam welder of appropriate capacity and embodying aligned electrode rolls, without requiring expensive additional equipment. The method can be carried out rapidly at relatively low cost, thus making possible the rapid and economical production of finned plates and the like.

Those skilled in the art will recognize that the method set forth in the appended claims may be practiced with apparatus embodying differences over that shown herein without departing from the scope of this invention.

I claim:

1. The method of simultaneously formin a weld between two members of one pair of metal members and another weld between two member of another pair of metal members with a single pair of roller welding electrodes to provide a series of individual spot welds including the steps of forming an assembly comprising the two pairs of members to be welded with one pair separated from the other by a highl current conductive metal plate having a substantial area of contact with each adjacent member and so positioned that the regions to be welded in each pair and the plate are in transverse alignment, positioning a roller welding electrode on each side of said assembly so each electrode makes rollin contact with one outer member of a pair at the region of the respective welds, engaging the edges of said plate with a plurality of guide rollers to guide the plate parallel to the plane of the electrode rollers, movin said rollers and said assembly relative to each other to cause the electrode rollers to traverse the regions to be welded and intermittently passing a welding current from one electrode roller to the other through said assembly to form a line of spot welds in the welded regions.

2. The method of simultaneously forming a weld between two members of one pair of ferrous metal members and another weld between two members of another pair of ferrous metal members with a single pair of roller welding electrodes to provide a series of individual spot welds, including the steps of forming an assembly comprising the two pairs of members to be welded with one pair separated from the other by a metal plate composed of a metal having substantially the current and heat conductive properties and softness of copper so positioned that the regions to be welded in each pair and the approximate center of the plate are in transverse alignment, positioning a roller weldin electrode on each side of said assembly so each electrode makes rolling contact with one outer member of a pair at the region of the respective welds and the electrode rollers lie in substantially the same plane transverse to said plate, engaging the edges of said plate with a plurality of guide rollers to 5 guide the plate parallel to the plane of the electrode rollers, resiliently urging said electrode rollers toward each other to apply welding pressure to the assembly, moving said rollers and said assembly relative to each other to cause the electrode rollers to traverse the regions to be welded and intermittently passing a welding current from one electrode roller to the other through said assembly to form a line of spot welds in the welded regions.

JOHN W. BROWN, JR.

REFERENCES CITED The following references are of record in the file of this patent:

Number 10 Number UNITED STATES PATENTS Name Date Knipe Aug. 22, 1911 DeGanahl Oct. 13, 1936 Heim Nov. 18, 1941 Watter Dec. 15, 1942 FOREIGN PATENTS Country Date France Sept. 1, 1942 

